Note that in the on-shell limit \(Q^2 = s + t + u = 0\)  we
reproduce the result for the scalar box given in Ref. [1]}.
\(\varepsilon \)  expansion of the scalar box diagram is discussed in
detail in Appendix REF . The results
for the other scalar box integrals are obtained via permutation
of Mandelstam variables \((s,t,u)\) .
Here we display important symmetry properties of the scalar box integral:
\(D_0(s,u,Q^2) &=& D_0(u,s,Q^2) = I_{0125}\,, \ \nonumber \\D_0(s,t,Q^2) &=& D_0(t,s,Q^2) = I_{0126}\,, \ \nonumber \\D_0(u,t,Q^2) &=& D_0(t,u,Q^2) = I_{0235}\,.\) 
